Are you using the New ULP (Universal Login Page) or the Classic one (the one with the login/signup tabs)?
In case it’s the New ULP: it’s currently not possible to directly jump to the signup page instead of the login page, but might available in the future. (I had asked this internally before about a month ago, because I had somebody asking me the same question, but at the moment it’s not possible. I added it to the product backlog though).
(It is possible wit the Classic login page though.)